So he's saying that Radaghast is a racist and horribly politically incorrect portrayal of a mentally handicapped black guy that everyone, including the characters in-universe and even his own people, loathed with a seething passion?

Yeah, no. At worst he's going to be a bit too comic reliefy, but he's very much just an old, eccentric wizard who might have a little trouble socializing with people. It won't even be remotely comparable.

Wait...JarJar Binks was a black stereotype? Where does this come from?